The present invention is directed to apparatus and methods for changing the color of a fluid such as paint and more specifically to apparatus and methods for changing the color of a flow of fluid, such as paint.
Conventionally, water-borne paint is produced in a batch process. In a typical batch process, such as that disclosed in U.S. Pat. No. 4,403,866 to Falcoff et al. (which is hereby incorporated by reference), paint components are metered into a large mixing vessel where they are mixed together by a mechanical mixer with a rotating blade or impeller. A formula for the paint determines the initial amounts of colorants, binder and other paint components that are added to the mixing vessel. Due to variations in the properties of the colorants and other paint components, the color of the paint produced from the initial components may not be within a certain color tolerance value as determined by ΔE. Accordingly, a small sample of the paint is removed from the mixing vessel and its color is measured with a spectrophotometer. If the color of the paint is not within the color tolerance value, additional amounts of colorants are added to the paint in the mixing vessel. This cycle of sampling, analysis and addition is repeated until the color of the paint is within the color tolerance value. Once this occurs, the process is complete and the paint is pumped from the mixing vessel to a holding tank or a filling station. With this type of batch process, the color of the entire batch of the paint is adjusted only by adding colorants to the mixing vessel.
Recently, it has been proposed to produce colored coatings in a continuous process. For example, U.S. Pat. No. 6,010,032 to Vermylen et al. (which is hereby incorporated by reference) discloses a method and apparatus for continuously producing a colored coating, such as a paste, for use in the continuous production of a coated, dyed, printed, or painted material, such as carpeting. The method and apparatus of the Vermylen et al. patent, however, does not have a system for monitoring and adjusting the color of the colored coating during its production.
Based on the foregoing, there is a need in the art for a method and apparatus for adjusting the color of a flow of fluid, such as paint. The present invention is directed to such a method and apparatus.